Porcelain Stoneware Research Articles

Integrated process simulation of porcelain stoneware manufacturing using flowsheet simulation

Integrated simulation of manufacturing plants plays crucial role in development of sustainable processes and optimized products. However, no investigation has been reported for the whole process chain of porcelain stoneware manufacturing. In this contribution, semi-empirical models of porcelain stoneware processing steps have been developed and implemented into Dyssol framework. By validation based on industrial and lab-scale experiments, the simulation has been applied for modeling and sensitivity analysis of the entire process. The simulation results are in a good agreement with experiments showing that the proposed modeling strategy has high potential to be used for future digital transformation in this sector.

Effect of strong mineral fluxes on sintering of porcelain stoneware tiles

Strong fluxes are needed to fire vitrified ceramics at temperatures significantly lower than those usually reached in industrial firing cycles. This work is aimed at understanding the role of strong fluxes in the microstructural evolution during sintering. Six fluxes (colemanite, ulexite, wollastonite, diopside, spodumene and phonolite) were individually added to a porcelain stoneware batch and processed in standard conditions. Compacts and fired bodies were characterized by optical dilatometry, XRD-Rietveld, SEM and measuring technological properties. Strong fluxes change the firing behaviour with a complex interplay of sintering kinetics, microstructural features, and phase composition. Every flux has its own repercussion on the properties of the liquid phase (chemical composition, degree of polymerization, viscosity and surface tension) which are key points to explain the observed microstructure, densification rates, and stability at high temperature. Batches with phonolite, wollastonite or diopside exhibit characteristics closer to standard porcelain stoneware, while spodumene and borates suffer from unsatisfactory microstructures and lower densification efficiency.

Effect of scale-up on the properties of PCM-impregnated tiles containing glass scraps

In the latest years, the interest about Phase Change Materials (PCM) in building applications grew in force of their capability to adsorb heat and limit in-out building heat exchanges. The main problem is how to introduce PCM into the building envelope, also in case of ventilated façades. For this purpose, a ceramic foam was studied. Two different batches based on porcelain stoneware and soda-lime glass scraps were prepared to understand the involved bloating phenomena. Suitable bulk density and porous microstructure were achieved by adding a foaming agent and batch optimization. Specimen size was scaled up (from ∅ 3 cm to 15 × 15 cm) and its effect on bloating, PCM incorporation, and thermal properties was studied. Furthermore, different firing temperatures and heating rates were evaluated. The whole study was focused to disclose possible drawbacks in the industrial transfer of the PCM-bearing composite production.

Adesione Additives for the Production of Asphalt Concrete with the Use of Waste in Building Ceramics

The possibility of using industrial waste is theoretically justified porcelain stoneware as an asphalt concrete filler. The influence of adhesive additives for bitumen bond BND (oil road bitumen) 60/90 with porcelain stoneware of various fractional composition has been established.

Solid state field-assisted silver ion exchange in porcelain stoneware: A new route toward antimicrobial tiles?

The development of tiles possessing antimicrobial activity is of great technological and scientific interest to improve the functionality of a very widely used article. Also the current SARS-CoV-2 pandemic is drawing the attention towards materials or compounds able to inactivate the virus, silver being among all the most promising one.In the present work, field-assisted ion exchange process was used to functionalize porcelain stoneware by introducing silver into the material surface using a solid silver electrode. The application of a small direct electric current (10 mA cm−2) at 380 °C allowed to fasten silver diffusion. The penetration of silver into stoneware appears homogeneous and primarily involves an exchange between silver and sodium ions under the effect of the external electric current. Penetration depths approaching 120 μm can be obtained in only 5 min. Preliminary characterization revealed that the Ag-exchanged stoneware possesses a strong biocidal action against Staphylococcus aureus.

Improving the sustainability of ceramic tile-making by mixing spray-dried and dry-granulated powders

Current trends in the ceramic industry see an increasing interest on porcelain stoneware, by which is possible to produce large tiles and slabs. These products are manufactured by spray-dried powders, which have excellent technological properties but require high energy and water consumption. Dry-processed granulates allow to reduce such a consumption, but suffer from a different technological behavior. A solution to improve the environmental sustainability of ceramic tile-making is mixing powders prepared by the wet and the dry routes. The technological features of industrially manufactured mixed powders was investigated (rheological properties, compaction response and firing behavior) in order to point out advantages and possible pitfalls. Dry-processed and spray-dried granulates exhibit different distributions of size, shape and moisture that reflect on distinct rheological and compaction behaviors. Mixed powders show a more or less accentuated deviation from linearity between the end terms. This fact makes possible to add up to ∼50% dry granulates by keeping the technological properties close to current industrial bodies. Sparings of water, energy and CO2 emission for the milling and granulation stages are estimated for a mix 50% spray-dried and 50% dry-processed powders.

Mineralogical and technological properties of the Konya clays, Central Turkey

Konya clay occurrence is the biggest clay mine of Turkey, except for the Şile region (Istanbul, Turkey) clays, and crop out near the Doganhisar (Konya, Central Turkey). It was formed by alteration of the Na- and K-feldspars, and muscovitic micas; additionally, direct transportation of the sericitic/illitic clays from the metapelitic rocks of metamorphic basement into the Neogene depositional basin. X-ray diffraction (XRD) studies revealed that major constituents of the Konya clays are the quartz, kaolinite and illite with the subordinate amount of paragonitic mica, pyrite, rutile and the organic materials (lignite, peat). The main purpose of this study is to determine the ceramic properties of Konya clays fired at various temperatures. For this aim, the chemical and mineralogical composition of clays was determined by X-ray fluorescence (XRF) and XRD. Thermal analysis techniques are used to measure the physical changes on heating, namely differential thermal analysis (DTA) and thermo-gravimetric analysis (TG). Test samples have been prepared by pressing and firing in the range of 900–1200 °C. Linear shrinkage, water absorption, flexural strength and color values were done in order to characterize clays after firing. Particularly between 1150 and 1200 °C, a significant decrease was observed in water absorption values. All studied samples seem to be easily adaptable for dry pressing ceramic process. In particular, kaolinite and illite rich samples show the best technological behaviors. The addition of Konya clays could have been used in wall, floor and porcelain stoneware tiles and sanitaryware ceramic products.

Eco-friendly ceramic tiles: development based on technical and market demands

This work aimed to develop eco-friendly ceramic tiles employing by-products of porcelain stoneware manufacturing as raw material, based on three technical-economic premises: designing new products that respect the standards; avoid using by-products as raw materials in successful commercial products; and carry out a complete mapping of operational conditions to enable employing mathematical modeling as product development methodology. Using a simplex-centroid design for ternary mixtures, three kinds of porcelain stonewares by-products were evaluated: sludge from the treatment of effluents, raw waste, and chamotte. The by-products were investigated by thermogravimetric analysis, water absorption tests, mechanical properties as well as X-ray diffraction and fluorescence under different compression and firing conditions. Mathematical models were generated capable of describing the experimental parameters behavior. These models showed that many kinds of products could achieve the water absorption ranges provided by normative requirement varying the operational conditions and the mass composition. Based on that, three kinds of ceramic tiles were reproduced in laboratory, each one according to mass formulation and operational conditions indicated by mathematical models: a wall tile, a floor tile, and a porcelain stoneware tile. Technical characteristics were controlled during laboratorial reproduction and, after that, their results were compared to normative requirements. All developed products met the normative requirement. The results confirmed that it is possible to develop ceramic tiles only employing by-products of porcelain stoneware as raw material through mathematical modeling, respecting the proposed technical-economic premises established for the present work.

Fabrication and Performance Analysis of Porcelain Stoneware Tiles Incorporated With Labware Glass Cullet

This study reported the effects of labware glass cullet on the properties of porcelain stoneware tiles. Five formulations of porcelain stoneware tiles (containing 0, 3, 6, 9, 12% borosilicate glass cullet) were prepared by adopting three different sintering temperatures (1100o, 1150o, 1200oC). The physical, microstructural and mechanical properties were analyzed. X-ray diffraction analysis ensured the presence of different crystalline phases in the samples. Morphological analysis also confirmed the results obtained from the XRD analysis. However, the density of the specimens increased within their operating parameters. Addition of glass cullet in the tiles increased the kinetics of the sintering process resulting in lower open porosity. Water absorption value of the samples sintered at 1200oC remained within the tolerance limit (∼0.5%). The lowest water absorption value (∼0.10%) as well as the highest linear shrinkage value (∼8.9%) were observed in the sample containing 12% glass cullet. Moreover, the usages of 12% glass cullet resulted in improved mechanical properties in comparison with other synthesized samples, whereas the values of compressive strength, impact strength and hardness were 51.65 MPa, 36.90 psi and 7.22 MPa, respectively.

Development of optical, microstructural and mechanical properties of porcelain stonewares

New production systems developed in recent years made it possible to improve different aesthetic appearance and large sizes for porcelain stonewares. In order to produce these tiles, optical and mechanical properties of the porcelain stonewares should be improved. Optical and mechanical properties also related with microstructure. In this study, spodumene, alumina and zircon were used to improve the microstructure of the porcelain stonewares and consequently their optical and mechanical properties. The wear resistance of porcelain stonewares is the one of the most important mechanical properties. In this study, a different test method was used because the existing wear test methods on the tiles were insufficient. The solid particle impingement method using alumina particles was used to determine wear resistance of the porcelain stoneware bodies.

Ceramics based on concrete wastes prepared by spark plasma sintering

An effective utilization technique is required to recycle fine aggregate in concrete waste because the presence of residual waste cement reduces the quality of the recycled concrete. In this study, recycled aggregate powder (RAP) was prepared by milling Okinawan concrete waste and developing a ceramic compact with high flexural strength using the spark plasma sintering (SPS) method. The RAP raw material consisted mainly of calcite and quartz. The densification gradient of the sintered compact was uniform during sintering at 1123-1273K. At 1273K sintering temperature, Vickers hardness (HV) obtained a maximum of 393 along with 78.9MPa maximum flexural strength, which exceeded the porcelain stoneware tile ISO 13006 standards. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX) element analysis suggested that the inner structure constituted unmelted silica-rich sand particles and melted calcium-rich particles containing waste cement and fine aggregate with limestone. Therefore, it can be concluded that SPS progressed by the liquid-phase sintering phenomenon between sand particles and calcium-rich particles, which contributed to flexural strength and modulus improvement.

Investigation of the sintering kinetic and development of ceramic masses for obtaining large-format porcelain stoneware in the conditions of high-speed firing

The paper considers the resource and energy saving reserves in the production of large-format stoneware slabs. The possibility of replacing high-quality feldspars with materials of technogenic origin, such as the extraction and processing waste of various feldspar-bearing rocks of domestic deposits has been investigated. The possibility of sintering process intensification has been investigated, as a condition for the use of high-speed firing modes in the stoneware production. As a result of the carried out studies, the kinetic features of ceramic masses sintering with alkaline syenites, granites and pegmatite enrichment wastes as fluxing component were determined. The formation conditions of densely sintered materials with a complex of high operational properties have been determined. The expediency of replacing Turkish feldspars with waste products of alkaline syenites has been established, while the level of physical, mechanical and operational properties of stoneware slabs meets the requirements of international standards. It is shown that, the use of complex flux, including feldspar-bearing rocks waste and dolomite, provides a significant decrease in the firing temperature of products (up to 1150 °C) while maintaining a high level of properties of stoneware slabs of class BІa. The obtained data indicate the possibility of optimizing the heat treatment parameters from the view point of energy saving with the further use of alternative fluxes in the large-format stoneware production. On the example of using the alkaline syenites wastes, the optimal ratios of the clay and fluxing components of ceramic masses have been established to obtain products with a complex of high performance characteristics when burning white clays of different chemical and mineral composition, which is a necessary condition for using a wide range of decorating techniques stoneware slabs. The structural-phase features of materials obtained under the conditions of high-speed firing are established: the formation of finely dispersed acicular mullite, which plays the role of a reinforcing component, as well as high structural homogeneity and maximum compaction, as evidenced by a few individual small pores presence. The combination of excellent technical qualities and large dimensions opens up new possibilities for the use of stoneware slabs as structural elements (countertops, ventilated facades, insulating panels for the installation of electrical systems, etc.).

Evaluation of ceramic mechanical properties by Impulse Excitation Techniques: Effects of heating temperature and cooling rate

The characterization of the ceramic materials integrity without damage has become a major issue for many industrial sectors. In this context, a research study has been initiated to assess the influence of the firing conditions on mechanical strength behaviors of Porcelain stoneware and Terracottas specimens. A focus is made on a non-destructive characterization method to evaluate the residual mechanical stresses, based on the Impulse Excitation Techniques. The influence of the cooling rate (≈200 °C/min by air ventilation vs. controlled cooling at 50 °C/h) and the heating temperature (1160 °C vs. 1185 °C for Porcelain stoneware; 1100 °C vs. 1150 °C for Terracotta) have been highlighted. The effect of samples annealing at 700 °C with a heating and cooling rate of 50 °C/h was also evaluated.A significant variation of the internal friction (2.5 times less important with a controlled cooling) and a small variation of 2.0% of the Young and shear moduli of porcelain stoneware samples caused by the cooling rate variation was shown. The negative effect of the fast-cooling was also discussed on terracotta samples by a small decrease (2.7%) of the Young and shear moduli. This decrease caused by a fast-cooling is led to micro-cracks formation induced by the quartz allotropic transformation during the cooling.In the case of terracotta, the 50 °C increase of the heating temperature induces a significant increase of mechanical strength properties linked to the open porosity decrease.The internal friction calculation from Impulse Excitation Techniques are able to efficiently evaluate the heat treatment quality of a porcelain stoneware ceramic material which allows the detection of mechanical performance decrease generated by micro-cracks in ceramic products.

Sustainable Ceramic Materials Manufactured from Ceramic Formulations Containing Quartzite and Scheelite Tailings

In this study, we develop ceramic formulations based on quartzite and scheelite tailings collected from mining companies in the northeast of Brazil (Rio Grande do Norte State). New ceramic samples (27 wt% of kaolin, 29 wt% of plastic clay, 11 wt% of quartzite tailing, and 0–8 wt% scheelite tailing) were uniaxially pressed in two steps (20 MPa and 50 Mpa for 20 s); dried at 110 °C for 24 h; and sintered at 1150 °C, 1200 °C, and 1250 °C. The main mineralogical phases (mullite, quartz, calcite, and anorthite) of the sintered samples were identified using X-ray diffraction (XRD). After evaluation of the physical-mechanical properties (water absorption, linear shrinkage, apparent porosity, and flexural strength), it was observed that the incorporation of scheelite tailing by up to 8 wt% did not significantly alter the properties of samples sintered at all temperatures. Our results indicate that the new ceramics formulations developed have strong potentials in manufacturing sustainable materials such as ceramic tiles and porcelain stoneware.

The effect of enrichment on quartz sand properties

The technological properties of quartz sand (without and after enrichment) by methods of emission spectral analysis, petrography, and X-ray phase analysis are investigated. The studied sand is a waste after extraction of titanium-containing components from raw materials. It is shown that the enrichment of quartz sand expands the field of its application. It has been established that quartz sand can be used as a filler of heavy, light, fine-grained, cellular and silicate concrete, mortar, and the preparation of dry construction mixtures. Also, sand can be claimed as a raw material component to produce ceramic tiles, porcelain stoneware, glazed ceramic products, wall ceramics, as well as proppants. Hydraulic enrichment leads to a decrease in the content of clay particles in the sand, which allows it to be used also for the construction of bases and coatings of roads and airfields. The integrated use of raw materials and waste allows solving the problem of creating non-waste and environmentally friendly technologies, which ensures the saving of natural raw materials, and on the other hand, allows it to be disposed of, improving the environmental situation.

Relationship between microstructure and the impact resistance of porcelain stoneware tiles

In this study, the variation of microstructural properties in porcelain stoneware tiles was determined by changing the holding time at peak temperature during sintering, and effects of these microstructural changes on impact resistance of porcelain stoneware tiles were examined. Only the F4 samples passed the impact resistance test according to CSTB-NF-UPEC test. This sample has 12.3wt.% quartz, 1.5wt.% corundum, 5.8wt.% anorthite, 13.5wt.% mullite, and 66.9wt.% glassy phase. When the relationship between mechanical properties and impact resistance was evaluated, it should be emphasized that only F4 sample with a breaking strength higher than 75MPa passed the impact test. It can be said that there is a critical threshold in terms of impact resistance, especially for samples which have bending strength greater than 75MPa. When evaluating the microstructural details, this study shows that a single crystalline phase is not effective for impact resistance behavior of the porcelain stoneware tiles and many factors should be evaluated together.

TiO2 coatings on the surface of buildings structural elements

The article presents the results of a study of the photocatalytic activity of coatings based on titanium dioxide on various structural elements of buildings. Fine-grained lightweight concrete, porcelain stoneware and window glass were used as a base. TiO2 coating was applied by reactive magnetron sputtering. The structure and phase composition of the coatings were investigated by scanning electron microscopy and X-ray phase analysis. The photocatalytic activity of the samples was evaluated according to ISO 27448: 2009 and ISO 10678: 2010. The photocatalytic efficiency of the obtained TiO2 coatings on building materials is shown. The data obtained allow us to make a preliminary assessment of the effectiveness of the application of this method of applying photocatalytic coatings to structural elements of buildings, which will be clarified in the course of future studies.

Glassy wastes as feldspar substitutes in porcelain stoneware tiles: Thermal behaviour and effect on sintering process

In view of the transition to circular economy, the ceramic industry is searching for suitable flux substitutes. Glassy wastes are promising candidates, even though they may significantly affect the firing behaviour and particularly high temperature permanent deformations. The goal of this study is to assess the sintering behaviour of porcelain stoneware bodies containing glassy wastes. Five different sources (bottle, PC-TV screen, lamp, frit manufacturing and porcelain stoneware grinding) provided glassy wastes that were separately added to a reference batch (20-40-60%) in substitution of feldspars. Each batch was characterized from the chemical point of view and its sintering kinetics were determined in isothermal conditions by optical thermo-dilatometric analysis. The quantitative phase composition after firing was determined by XRD-Rietveld in order to calculate chemical and physical properties of the vitreous phase at high temperature. The substitution of feldspathic fluxes determines a clear change in the firing behaviour: waste glasses lower the temperature at which the densification starts, and extend the early stage occurring before a constant rate sintering takes place. In some cases, the deviation is important and entails a lower sintering efficiency. The reasons behind this different firing behaviour are discussed in terms of composition, structure, and properties of the melt.

Powder rheology and compaction behavior of novel micro-granulates for ceramic tiles

Using spray-dried powders is widely consolidated in ceramic production, especially for porcelain stoneware tiles and slabs. However, a novel micro-granulation process can reduce the consumption of water and energy. It is based on wetting-agglomeration-drying operations that can be managed either as dry (dry-milled powders, micro-granulation) or hybrid route (wet-milled slurry and dry-milled powders, micro-granulation). The goal is to compare these new dry and hybrid micro-granulates with conventional spray-dried and dry-granulated powders by determining: grain size, shape and moisture distribution; static and dynamic angles of repose; poured and tap density, Hausner ratio; mass flow rate; compaction response; microstructure, pore size distribution and yield strength. The new micro-granulates exhibit improved rheological performances, approaching under some manufacturing conditions those of spray-dried powders, particularly in case of the hybrid route. Differences persist in compaction behavior: this is the consequence of distinct microstructure, porosity and stiffness of spray-dried agglomerates and dry/hybrid micro-granules.

Effect of Chemical Composition of Glassy Phase of Porcelain Stoneware on Product Brittleness

During the operation of porcelain stoneware sometimes there is a type of defects associated with crumbling from the edge of tile. In addition, cracks occur when a small object is fallen and during transportation of the products. Compared to conventional ceramic floor tiles, porcelain stoneware has increased strength, which explains its high price. The brittle failure is most likely, due to the hardening of glassy phase of tiles during cooling stage of the firing process. As a rule, the quenching temperature depends on the chemical composition of the glassy phase formed during firing. Both the phase and chemical composition of porcelain stoneware, and the chemical composition of the glassy phase are determined.